In typical cellular wireless communication systems, wireless communication devices (e.g., cell phones, personal digital assistants, laptops, netbooks, tablets, and/or other wirelessly equipped devices, any of which may be referred to as a user equipment device (UE) for brevity) subscribe to service from a given cellular wireless service provider. In practice, a service provider will operate one or more networks (sometimes referred to as radio access networks (RANs)) including base stations that radiate to define one or more wireless coverage areas, referred to as sectors, where the subscriber UEs can operate.
Through each base station (and corresponding RAN), a UE can obtain connectivity to other networks such as the public switched telephone network (PTSN) and the Internet. Further, each RAN may include one or more radio network controllers (RNCs), or the like, which may be integrated with or otherwise in communication with the base stations, and which may include or be in communication with a switch or gateway that provides connectivity with one or more transport networks. Conveniently with this arrangement, a UE that is positioned within coverage of the RAN may communicate with a base station and in turn, via the base station, with other served devices or with other entities on the transport network.
Generally, wireless communications between a given UE and a serving base station in a RAN are carried out in accordance with one or more air interface protocols that define a mechanism for wireless exchange of information between the UE and the base station. Typically, an air interface protocol will define a “downlink” encompassing communications from the base station to the UE and a “uplink” encompassing communications from the UE to the base station. Further, each of these links may be structured to define particular channels on which certain types of data may be transmitted. These channels may be defined through the use of various mechanisms, including for example, time division multiplexing, code division multiplexing (e.g., spread-spectrum modulation), frequency division multiplexing, as well as others.
The downlink, for example, may define (i) a pilot channel on which the RAN may broadcast a pilot signal to allow UEs to detect wireless coverage, (ii) system parameter channels (e.g., an overhead channel) on which the RAN may broadcast system operational parameters for reference by UEs so that the UE can then seek network access, (iii) paging channels on which the RAN may broadcast page messages to alert UEs of incoming communications, and (iv) traffic channels on which the RAN may transmit bearer traffic (e.g., application data) for receipt by UEs. And the uplink, for example, may define (i) control channels on which UEs may transmit registration messages and call origination requests, and (ii) traffic channels on which UEs may transmit bearer traffic for receipt by the RAN.